Blacker than Black

textfilter: chose text/plain from a multipart/alternative

http://www.nasa.gov/topics/technology/features/super-black-material.html

They talk about all the instrument uses and the uses in heat management.
However, I'm wondering if a coating of this would help stealth satellites,
drones, and spaceplanes... maybe even starships....

> On Tue, Nov 08, 2011 at 05:06:30PM -0500, Tom B wrote:

> http://www.nasa.gov/topics/technology/features/super-black-material.htm

By making them _more_ efficient emitters of infra-red?

If they were purely passive and produced no waste heat, perhaps...

R

You forget, Mister Burton West, how we're all about countering Mk. I
eyeball. ;->=

Doug

From:	Roger Burton West <roger@firedrake.org>
To:	gzg@firedrake.org
Date:   11/09/2011 03:42 AM
Subject:	Re: Blacker than Black

> On Tue, Nov 08, 2011 at 05:06:30PM -0500, Tom B wrote:

> http://www.nasa.gov/topics/technology/features/super-black-material.htm

By making them _more_ efficient emitters of infra-red?

If they were purely passive and produced no waste heat, perhaps...

R

> On Wed, Nov 09, 2011 at 06:48:29AM -0600, Doug Evans wrote:

Oh, now that's a scream; never heard that!

Gives whole new meaning to 'make like a hole...'

Thanks, and sorry to all for the derailment of thread.

Doug

From:	Roger Burton West <roger@firedrake.org>
To:	gzg@firedrake.org
Date:   11/09/2011 06:59 AM
Subject:	Re: Blacker than Black

> On Wed, Nov 09, 2011 at 06:48:29AM -0600, Doug Evans wrote:

I can't help remembering that rumour about the Ohio-class SSBN - that
when first in service, they were sufficiently _quieter_ than the
equivalent volume of seawater that it actually made them easier to
track...

R

RB-W:
By making them _more_ efficient emitters of infra-red?
If they were purely passive and produced no waste heat, perhaps...

FTA: "The reflectance tests showed that our team had extended by 50 times the
range of the materials absorption capabilities. Though other
researchers are reporting near-perfect absorption levels mainly in the
ultraviolet and visible, our material is darn near perfect across multiple
wavelength bands, from the ultraviolet to the far infrared," Hagopian said.
"No one else has achieved this milestone yet." In particular, the team found
that the material absorbs 99.5 percent of the light in the ultraviolet and
visible, dipping to 98 percent in
the longer or far-infrared bands. "The advantage over other materials
is that our material is from 10 to 100 times more absorbent, depending on the
specific wavelength band," Hagopian said.

TB: That was the part that had my attention. FTA the reprise: Black materials
also serve another important function on spacecraft
instruments, particularly infrared-sensing instruments, added Goddard
engineer Jim Tuttle. The blacker the material, the more heat it
radiates away. In other words, super-black materials, like the carbon
nanotube coating, can be used on devices that remove heat from instruments and
radiate it away to deep space. This cools the instruments to lower
temperatures, where they are more sensitive to faint signals.

TB: Admittedly, I'm confused now. It is 98% absorptive in infra-red,
but it also radiates away more heat... I can't quite reconcile this in my
head.

I was imagining that there was some way to use the absorptive effect to such
up active signals such as radar or lidar (and not give a bounce back). On the
heat front, I thought perhaps it could be used somehow to direct heat output
where you wanted it or absorb it (admittedly, since I can't reconcile highly
absorptive and highly radiative, the how is fuzzy to me...).

Tom B schrieb:
> TB: Admittedly, I'm confused now. It is 98% absorptive in infra-red,

Indeed, this seems like a paradox, but actually, it's true.

It may help to think about it as two different processes. One is how the

surface handles incoming radiation, the other is how it sends radiation
generated by the object.

When we call an object black or white, we refer to the way it handles incoming
radiation. A white object reflects radiation, a black one absorbs it. Note: of
course this also depends on the incoming light. At night everything looks
black, because there is no light around.

Any object above absolute zero temperature also sends out heat radiation. It
is in the infrared at normal temperatures, but if you heat

it up, it starts to glow in visible light.

By a paradoxic-seeming twist of the laws of physic, a black object is
both the best absorber of incoming radiation and the most efficiet emitter of
outgoing heat radiation.

I hope this helps Greetings Karl Heinz

textfilter: chose text/plain from a multipart/alternative

Emission and absorption are basically the same process in reverse. The
material properties determine how efficient the material is at
absorbing light - with the remainder being reflected.

In the reverse process it determines how much energy is emitted as light and
how much is retained internally.

Hope this makes sense.

Derk

Sent from my HTC

----- Reply message -----
From: "K.H.Ranitzsch" <kh.ranitzsch@t-online.de>
Date: Fri, Nov 11, 2011 7:03 am
Subject: Blacker than Black
To: <gzg@firedrake.org>

Tom B schrieb:
> TB: Admittedly, I'm confused now. It is 98% absorptive in infra-red,

Indeed, this seems like a paradox, but actually, it's true.

It may help to think about it as two different processes. One is how the

surface handles incoming radiation, the other is how it sends radiation
generated by the object.

When we call an object black or white, we refer to the way it handles incoming
radiation. A white object reflects radiation, a black one absorbs it. Note: of
course this also depends on the incoming light. At night everything looks
black, because there is no light around.

Any object above absolute zero temperature also sends out heat radiation. It
is in the infrared at normal temperatures, but if you heat

it up, it starts to glow in visible light.

By a paradoxic-seeming twist of the laws of physic, a black object is
both the best absorber of incoming radiation and the most efficiet emitter of
outgoing heat radiation.

I hope this helps Greetings Karl Heinz

textfilter: chose text/plain from a multipart/alternative

On Fri, Nov 11, 2011 at 1:03 AM, K.H.Ranitzsch
<kh.ranitzsch@t-online.de>wrote:

> Tom B schrieb:
At
> night everything looks black, because there is no light around.

An experiment for the student: take two similar objects, one black, one white,
and place them out in the sun for an hour or three (really, just for a long
while). Note which one is warmer. Now take them out of the sun. Let sit for a
few minutes. Note which one is warmer (but is cooling off quickly as it
radiates away).

:-)

Mk

textfilter: chose text/plain from a multipart/alternative

You know there's one sensor that can't be jammed, but it's not that accurate
fer fire control. It's gravity sensors.

________________________________
From: Derk Groeneveld <derkgroe@xs4all.nl>
To: gzg@firedrake.org
Sent: Friday, November 11, 2011 2:47 AM
Subject: Re: Blacker than Black

textfilter: chose text/plain from a multipart/alternative

Emission and absorption are basically the same process in reverse. The
material properties determine how efficient the material is at
absorbing light - with the remainder being reflected.

In the reverse process it determines how much energy is emitted as light and
how much is retained internally.

Hope this makes sense.

Derk

Sent from my HTC

----- Reply message -----
From: "K.H.Ranitzsch" <kh.ranitzsch@t-online.de>
Date: Fri, Nov 11, 2011 7:03 am
Subject: Blacker than Black
To: <gzg@firedrake.org>

Tom B schrieb:
> TB: Admittedly, I'm confused now. It is 98% absorptive in infra-red,

Indeed, this seems like a paradox, but actually, it's true.

It may help to think about it as two different processes. One is how the

surface handles incoming radiation, the other is how it sends radiation
generated by the object.

When we call an object black or white, we refer to the way it handles incoming
radiation. A white object reflects radiation, a black one absorbs it. Note: of
course this also depends on the incoming light. At night everything looks
black, because there is no light around.

Any object above absolute zero temperature also sends out heat radiation. It
is in the infrared at normal temperatures, but if you heat

it up, it starts to glow in visible light.

By a paradoxic-seeming twist of the laws of physic, a black object is
both the best absorber of incoming radiation and the most efficiet emitter of
outgoing heat radiation.

I hope this helps Greetings Karl Heinz

Let me sum up the understanding people have tried to beat into my head with
the required Power Axe:

Black things will absorb the most incoming radiation: Good for stealth. Black
things will also readily radiate any heat they may themselves generate: Bad
for stealth.

Hmmm. I begin to understand further (already knew telescope arrays could be
good at differentiation from cosmic background) why stealth
is tough in space - the thing that makes active sensors less effective
against you (absorption) may well make you radiate heat like a sonofagun.

I guess this explains to some extent why many stealth planes and ships put a
premium on surfaces angled to bounce incoming radar waves away in some
orthogonal direction rather than directly back at the emitter (and thus
presumably at the reciever).

It doesnt exactly tell me why the B2 and F-117 were black (if this is
crappy for thermal stealth), but perhaps the radar threat and visual
observation issues were more critical than thermal stealth in the design
process.

Tom B schrieb:

> I guess this explains to some extent why many stealth planes and ships

I assume that the stealth planes are black because they are supposed to
operate at night and black provides visual camouflage.

Note that there is a significant difference between heat radiation in
space and on earth. Space is *cold* - some 3 degrees above absolute
zero. Any object warmer than that is a net radiator.

On Earth the athmosphere and every object is warm, some 270 degrees Kelvin,
and everythings radiates heat and receives heat radiation from everything
else. So if something is at room temperature it will not register on aheat
sensor. So thermal camouflaging is easier on Earth.

Greetings Karl Heinz

textfilter: chose text/plain from a multipart/alternative

There is no technical reason for stealth planes being black. In fact
skunk works had them in a blue-gray and pink-gray to fade into dusky
skies, but the perforce did not think that was manly and decided on sexy black
instead.

Derk

Sent from my HTC

----- Reply message -----
From: "Tom B" <kaladorn@gmail.com>
Date: Sat, Nov 12, 2011 7:32 am
Subject: Blacker than Black
To: <gzg@firedrake.org>

Let me sum up the understanding people have tried to beat into my head with
the required Power Axe:

Black things will absorb the most incoming radiation: Good for stealth. Black
things will also readily radiate any heat they may themselves generate: Bad
for stealth.

Hmmm. I begin to understand further (already knew telescope arrays could be
good at differentiation from cosmic background) why stealth
is tough in space - the thing that makes active sensors less effective
against you (absorption) may well make you radiate heat like a sonofagun.

I guess this explains to some extent why many stealth planes and ships put a
premium on surfaces angled to bounce incoming radar waves away in some
orthogonal direction rather than directly back at the emitter (and thus
presumably at the reciever).

It doesnt exactly tell me why the B2 and F-117 were black (if this is
crappy for thermal stealth), but perhaps the radar threat and visual
observation issues were more critical than thermal stealth in the design
process.

Tom

To summarise the summary:

To defeat active sensors, the stealthed object must not reflect in the range
used by the sensor. The Mk1 eyeball is the receiving element of a bistatic
active system, with the transmitting element usually being the Sun, but other
light sources can be substituted, on an ad hoc basis.

To defeat passive sensors, the stealthed object must not radiate more than
whatever is behind it, relative to the observer. Glowing hot steel in a
glowing hot furnace furnace can be hard to see, once it has matched
temperatures. With the background temperature of space being about 3K, hiding
from infrared sensors is hard. With Earth's atmosphere at about 273K, infrared
stealth is easier.

The brightness of infrared emissions is proportional to the fourth power of
the temperature, so a stealthy object needs to radiate away

> On Sat, Nov 12, 2011 at 04:05:31PM -0700, Richard Bell wrote:

As one U.S. General is reported to have said when trying to understand why SDI
wasn't going to be practicable on a large scale: "Whoever came
up with these laws of physics is some kinda god-damned commie!"

R

textfilter: chose text/plain from a multipart/alternative

To further complicate issues - waste heat disposal can be a bit of a
problem in space. On Earth you have thermal conduction, convection and
radiation to all help get rid of waste heat, but in space all you've got is
radiation. If you want your spacecraft doing anything it will generate
waste heat - and it has to go somewhere otherwise your spacecraft will
just get warmer and warmer. Since it has to go into radiation you will have to
present a bright thermal signature.

The first thing I thought when I saw the pictures of the material was that
those tubes make really good black body cavities.   It turns out the
perfect emitter/absorber is a small cavity in a surface (perfect
absorber
because any light that enters will bounce around until absorbed/perfect
emitter is a little harder to explain - I finally found a good way to
present it in my modern physics class last year.) It doesn't even matter
if the material is reflective or not - the cavity will eventually absorb
the light. Those little nanotube basically act as little cavities in the
surface. Pretty neat in my opinion, even if it isn't a magical stealth
material for spacecraft.

On Sat, Nov 12, 2011 at 5:05 PM, Richard Bell

I had thought space was (for the most part) temperature-less rather
than cold. As I understood it, near vacuum i slow in molecules and temperature
is effectively a result of molecules absorbing thermal energy.

This explanation seemed to cover why the space shuttle can't get rid of heat
easily (no convenient molecules to radiate things away to by contact) and it
covered why space is seen as 'cold' (few molecules to aboorb heat per unit
volume).

Of course, this doesn't cover radiation via waves very well, but I figured
that they still weren't temperature until they transferred their energy to a
molecule (ie that an infrared wave was effectively not by itself 'hot' until
such time as it was transferring the energy to a molecule, it wasn't really
temperature). I sort of thought of this as the difference between potential
energy and kinetic energy (potential energy for instance, would not be easily
observable, while kinetic energy in the form of a moving object, would be).

That understanding is probably incorrect, but it did seem to cover most of the
bases in some fashion.

The reason I am curious about stealth in space being so hard: I agree that
camouflage in all spectra is harder against a negligible background. Light
sources in space are point sources (so are heat and
x-ray sources and perhaps general EM, but that's a bit vaguer to me as
there is a level of cosmic background radiation that seems to suggest general
EM is 'all over the place'). So for the most part, hiding using any of them as
background would require either being (and staying) in LoS between potential
observer and background cover (tough in a moving universe, but perhaps not
impossible) or else simply having the searcher miss you.

Now, you say to the last one: What?

I sort of think of the Mark I eyeball connected to the brain. We do a lot of
looking around us for threats and oddities which might be threats. But we
still often fail to note stuff. Part of this is the visual complexity of our
enironment, part of it our level of distraction, and part of it not
recognizing certain risks as to what they are.

So how is that transferrable to space:

1. I assume that sensor have a certain sensitivity. If they aren't good
enough, they might not see the threat, given certain assumptions about how
visible it is and how capable they are.

2. I assume sensors have a certain scan rate - how fast they can sweep
an area of space.

3. Sensors may be subject to depth issues (I'm not sure if such sensors
instantly see everything at all depths equally well or need to scan varying
depths meaning more scan passes to determine accurately
what might be thee). Space is 3-D and perhaps like the Mk I eyeball, a
sensor has to focus on areas close, medium or far to get accuity.

4. Data processing systems are finite and must process the scan data. If they
have to process different wavelengths or energy types seperately, that
magnifies the task. Perhaps they can only process accurately a portion of the
total depth, energy types, or spherical segments of the sky. If the rate at
which they can scan those regions with high enough accuity is low enough, then
that opens a window for stealth.

5. Similar to how a human may be distracted, ships may have other complex
activities to carry out such s handling jump drives, power cores, nav calcs,
and other such things. This may limit how many of the finite compute resources
can be tasked to processing scan data. This may be doubly true at times when a
threat is not known to be out there (at battle alert levels, scan processing
may get a fairly high priority from the task engine). So this may impede
ability to detect by virtue of limiting processing time or accuity.

6. Much like a human trying to hear a conversation in a bar, if there happen
to be a pile of other noises going on in the bar, the human won't hear. If
there are a pile of ships emitting in local space (merchants, other warships,
buoys, etc) plus natural sources, then maybe there is a lot of signal bouncing
around in various spectra that could confuse the issue. In terran ESM
(Electronic Signal Measures), one of the big challenges is knowing, from
moment to moment, what a potential bit of contact data means. Are two data
points referencing the same thing? Maybe, maybe not. Is there enough to tell
if they are the same class? Maybe, maybe not. Can they be spoofed? Perhaps.
Even if they are the clear sign of an enemy active system, they may not show
the same from emission to emission. If they are passive, is it two ships on
slightly variable courses or one ship? Is it civilian or military? The other
side of ESM is worried about confusing people by virtue of spoofing (having
your frigate emit signature like a commerical hauler, for instance). Now, on
Earth, this happens in busy waterways where it is the worst. It also happens
with some itnerference from weather and seas. And incomplete data in the first
place as to what the enemy's signature may be.

So, I was wondering what the aggregation of these factors is actually going to
do to detection. Space right now around our world is fairly empty (except
directly in orbit, full of junk). If space was busy with lots of civilian
shipping and spoofing might be in play, how much harder would that make
things? If you had to try to scan everything from Earth Orbit to out beyond
(whatever object we call the farthest planet in our system these days.... poor
Pluto!), can you actually process all of that fast enough to tell you what you
need to know at
all ranges? And not 'what can you do with the science-specific
platform' but what can you do with the system installed on a typical warship?

Traveller: New Era made a big deal out of your sensor system size in detecting
objects. It had unfoldable arrays and the bigger your array, the more you'd
take in. But unfolding an array took time and if you ended up having to move
quick or get shot at, I imagine it could be damaged. Without the array out,
your sight (electronically speaking) would be very limited.

So, what can we practically expect to see in these environments? Is it
possible we will miss or dimiss contacts that are threatening? Is it
possible we will mis-classify incoming traffic? Is it possible we will
not be able to process enough of the sky to see a new object before it becomes
dangerous?

That's what I still don't quite understand. Stealth when someone has the
resources to look right at you, at whatever range you are at, and process that
data without distraction, I accept as being difficult. But is real stealth,
which includes the effects of 'friction' (in the Clausewitzian sense) on
detection systems and those involved in interpreting their data, actually
impractical?

Maybe I can't sneak up easily on your frontier outpost if it has top of the
line sensors. But maybe it often doesn't because it is a frontier outpost.
Maybe sneaking up on your shipping hubs and typical busy systems with space
commerce is much easier.

Thoughts?

> On Sun, Nov 13, 2011 at 03:21:51PM -0500, Tom B wrote:

> 3. Sensors may be subject to depth issues (I'm not sure if such

For a precise image, sure. But to say "hey, there's something in that
direction, time to take a closer look" on the IR sensor, all you need is a bit
of directionality on your IR photodiode.

Are you perhaps conflating detection with lock-on? When I talk about
stealth, I'm thinking mostly about concealing the fact that there's a target
there at all. That's really not doable in space. To use your Mk I eyeball
analogy, it's dark, everyone out there is covered in bright white LEDs, and
there's nothing to hide behind.

But throwing out multiple targets and confusing the systems that are pointing
weapons at you? Much more plausible. You're still walking around covered in
LEDs, but you can leave candles behind as you go.

R

textfilter: chose text/plain from a multipart/alternative

One point here in this thread. Not so much about stealth, but detecting an
object at all. How large are spaceships presumed to be, and how close must
they get before the current technology of the time (or colony) can see them at
all, much less resolve them with any detail? The sky is a vastly enormous
volume to be looking for an intruder speck in on a constant basis. And not
every random rock (asteroid of small size) is likely to have been cataloged
without a *tremendous* amount of work, in any given system (then there are
always the oddballs that randomly appear).

On the flip side, how much energy output are ships doing when they are
thrusting in-system from wherever they jumped? Asteroids are whizzing
about a mach speeds, but on a solar system scale, painfully slow crawls.
Certainly no intruding ship is going to try and take a year or three to get
to where it wants to go.  ;-)

Mk

On Sun, Nov 13, 2011 at 3:40 PM, Roger Burton West <roger@firedrake.org>wrote:

> On Sun, Nov 13, 2011 at 03:21:51PM -0500, Tom B wrote:

textfilter: chose text/plain from a multipart/alternative

Presumably ripping a hole in the material universe to jump in would cause some
kind of detectable emmission?

I'm not sure I remember how GZG canon describes warp space jumps. Is it like
star trek or starwars where ship travel takes time and ships therefor have
sensors that can detect other objects in the hyperspace environment and
possible in real space while in hyperspace? Or is it some kind of instant
blind jump where it's a pop in and out maybe like BSG and it's all down to
really complicated maths to predict the location of every knowm object in the
target system and there's no detection?

Is it possible for a ship in real space to detect an object in hyperspace? If
so does this create a submarine warfare kind of effect?

If so it makes all the discussions about real space detection rather moot.

Unless ships can jump relatively close to their destination it will take them
month's or years to get to an inner planet in a way that matches velocity with
the target planet. Vast amounts of reaction mass would be needed to accelerate
a ship and then deccelerate it at the other end of the journey.

textfilter: chose text/plain from a multipart/alternative

On Sun, Nov 13, 2011 at 11:05 PM, John Tailby
<john_tailby@xtra.co.nz>wrote:

> [...]

John G Hemry (of the Lost Fleet series that some on here know) shows this
quite well in his novels. To overcome the vast distances in a solar system, he
has all his combat happening at relativistic speeds of 0.1 to 0.2c. Still, it
takes hours and days to get into engagement range, and everyone can see
everybody sooner or later (he also deals with light travel time of how long it
takes before a defending unit will see an intruding fleet, just due to the
time it takes for the photons to get from the intruding ships to the defending
detectors).

Mk

textfilter: chose text/plain from a multipart/alternative

That's still a pretty difficult battle to arrange.

An invading fleet coming in system at.2c would take a couple of months to
reach earth from a realspace entry at the edge of the system.

A defending fleet based on an in system base would need to take off to
intercept and they want to intercept the enemy as far away as possible. If
they want some kind of sustained engagement then they need to match vector
with the attacking fleet, that is a pretty big delta.

If the attacking fleet wants to engage the target planet with anything other
than a brief flyby, then they need to spend a lot of energy to slow down to
the target planet velocity vector.

It also means that for a fleet to operate together they need the same thrust
capability. This is quite different from how GZG fleets are designed.

From: Indy <indy.kochte@gmail.com>
To: gzg@firedrake.org
Sent: Tuesday, 15 November 2011 3:41 AM
Subject: Re: Blacker than Black

textfilter: chose text/plain from a multipart/alternative

On Sun, Nov 13, 2011 at 11:05 PM, John Tailby
<john_tailby@xtra.co.nz>wrote:

> [...]

John G Hemry (of the Lost Fleet series that some on here know) shows this
quite well in his novels. To overcome the vast distances in a solar system, he
has all his combat happening at relativistic speeds of 0.1 to 0.2c. Still, it
takes hours and days to get into engagement range, and everyone can see
everybody sooner or later (he also deals with light travel time of how long it
takes before a defending unit will see an intruding fleet, just due to the
time it takes for the photons to get from the intruding ships to the defending
detectors).

Mk

On Mon, Nov 14, 2011 at 3:54 PM, John Tailby <john_tailby@xtra.co.nz>
wrote:
> It also means that for a fleet to operate together they need the same

Well, technically, one has to be able to match the other.

D.

> On 14/11/2011 04:05, John Tailby wrote:
 From the introduction to the FT2 rules, "[...] one of our far-orbit
sensors detected emergence diffusion effects characteristic of a large task
force of naval units dropping out of FTL drive [...]", so yes, FTL arrival can
be detected at a distance, presumably by STL methods (so they're not where you
see them, but they used to be).
> I'm not sure I remember how GZG canon describes warp space jumps. Is
More like the latter, if I read other background stuff correctly, notably the
description of a Jump from FB1. It's effectively instantaenous, with a
significant margin of error on the arrival end. Not sure that anything has
been stated one way or the other about any
limits to where you can arrive or depart from, so no Traveller-style
100-diameter rule that I am aware of. Against that, various background
pieces seem to have incoming ships arriving at the edges of a system, so

it may be there but not stated explicitly.
> Is it possible for a ship in real space to detect an object in
If so it makes all the discussions about real space detection rather moot.
They can't do it because the ship is only in "hyperspace" for an infinitesimal
instant, so you can't see it coming, but you do know when
it arrives -- eventually.
> Unless ships can jump relatively close to their destination it will
Only if you use a reaction drive. IIRC, normal space drives in the
GZGverse are some kind of field drive (effectively anti-gravity), so the

reaction mass isn't needed, just a big energy source. And we've discussed the
kind of accelerations that GZG ships can produce with their normal space
drives. It's all speculation, but if, as one
suggestion was, 1 thrust = 1g, ships have more than enough delta-V to
move freely around a star system without trouble and in reasonable time.

ISTR Heinlein writing that 1 g was enough to get from Earth to Pluto in a
week, so 8 g would allow ships to zip anywhere in a star system the size of
Sol in about 2.5 days. Of course, the trick is to be able to
sustain that thrust, but if you can, intra-system travel becomes
straight-forward and no more time-consuming than, say, a
transcontinental coach or train trip.

Phil